Why an AI plane doesn't keep it's flight level?

[PHo17]

I followed an AI plane (AI Ardwark's Boeing B755-200 PW i.e. WoA_AIA_B752_PW - Finnair paint) by Traffic View Board (attached to this aircraft) and found out some strange behaviour.

When the airplane reached it's flight level, it couldn't keep it. All the time it was rising or descending over or below the flight level the Traffic Control told it to keep. At the same time the speed of the aircraft was far less than it should have to be.

I checked the aircraft and flightplan files but found nothing exceptional (speed was as it should be and so on). The flightplan wasn't however World of AI's but Harri Heliövaara's for Finnair and winter 08-09.

Where should I look for the correction?

Pekka

[dhazelgrove]

What makes you think there is a fix?

If you're unhappy with the flight plan, then get a copy of AIFP (freeware) and fix it yourself.
You'll learn a lot that way.

Beware though - it's addictive!!

Dave

[dogknot]

A couple of things I would consider concerning the altitude hold and speed are:

AI aircraft will sometimes bob and weave if you get too close...I just consider it a rudimentary avoidance system.

Airspeed from the cfg and then the notations in the aircraft_***.txt file via ttools is computed in KTAS (Knots True) and not in KIAS (Knots Indicated). At flight level, the aircraft may seem to be flying slower than your indicated airspeed.

[Moparmike]

Another thing to watch for is if the flightplan speed and the AI plane used match fairly close.
Can the plane's airfile actually maintain the speed called for at the FL set in the plan?
Think of the alt and speed as autopilot settings for that particular AI flight.

It's kinda like trying to run a user plane on AP and speed hold in a range that it can't operate....the trim and throttle will be constantly fighting trying to maintain the AP settings.


Used to see the same thing when I was building missions for CFS2 too.

[tgibson]

Yep, some planes just do that. If flying too slow, the controller is the cruise speed value in the Reference Speeds section of the aircraft.cfg file.

Hope this helps,

[Lionheart]

Also, if your plane is on a route that it cannot meet in time on the schedule, it will appear to lose altitude and eventually crash and disappear into the ground.

Wild watching how the AI works.. Entertaining at times.

:d



Bill

[java2srv]

I had some of the HTAI Cessnas doing hops between Telluride and Durango and Cortez. I discovered they were flying along enroute with the flaps down. They have to get pretty high to clear the terrain according to the way FS9 does AI.

I "turbocharged" the planes by changing the aircraft.cfg to maintain sea level power (30 inches Manifold Pressure) up to about 18,000ft. That seems to have done the trick.

My guess is that the planes couldn't maintain altitude and airspeed, or that the indicated airspeed became so low that the aircraft deployed flaps. With the additional power the airspeed seems to have increased and the planes behaved like they were enroute again, instead of in the landing pattern.

Speaking of landing patterns. Since I fly in Colorado a lot I've had to get creative a time or two in order to get AI into and out of some of the small fields up in the Rockies.

I'm using Mike Stone's Spartan for some AI air taxis, and in order to get them into Glenwood Springs I created an AFCAD file for the airport that adjusted the traffic pattern altitude so the AI planes weren't flying through the surounding terrain and disappearing. Put some time and some trial-and-error into that one.

:wiggle:

[PHo17]

I had some of the HTAI Cessnas doing hops between Telluride and Durango and Cortez. I discovered they were flying along enroute with the flaps down. They have to get pretty high to clear the terrain according to the way FS9 does AI.

...

:wiggle:

I tried again - and indeed the flaps ware full down like in landing positions! Indicated KIAS was about 190 (other traffic passed by very fast).

I know the basics of AI and have done some AI traffic (from scratch) myself too. So I am pretty sure that there is nothing wrong with the flightplans or other AI files.

I guess it must be something to do with the aircraft or FS9 AI handling as you say. However this is the first of this kind of oddness I met (there is a plenty of curiousities in FS9 AI).

What is the thing in the aircraft.cfg I should change?

Pekka

[java2srv]

I found the changes that I made to the HTAI Cessna 206 and 207 aircraft.cfg files. I would have posted the changes above but I was away from the flight sim PC. Apologies for leaving that hanging in mid air.

Changes are in 4 lines in the [piston_engine] section in the aircraft.cfg file.

[piston_engine]
turbocharged=1 //Is it turbocharged? 0=FALSE, 1=TRUE
max_design_mp=38 //Max design manifold pressure, (inHg)
min_design_mp=1 //Min design manifold pressure, (inHg)
critical_altitude=18000 //Altitude to which the turbocharger will provide max design manifold pressure (feet)

Of course this is only applying to a piston single engine General Aviation aircraft, the Cessna 206. No changes to the .air file.

Most of my AI are small planes like the Cessnas. I do not know how I would go about changing the engine section for a jet airliner.

I also have the Cal Classics propliner AI planes. Jet airliners have been left mostly as the default AI that comes with FS9.

I am familiar with the AI Aardvark web site and have some of their smaller jetliners waiting to take over AI duties. I don't have anything from World of AI so I don't know about the 755-200. Sorry. Perhaps try the .air and the aircraft.cfg files from the original equivalent AI Aardvark B755?

:wiggle:

[PHo17]

I found the changes that I made to the HTAI
...
Most of my AI are small planes like the Cessnas. I do not know how I would go about changing the engine section for a jet airliner.

I also have the Cal Classics propliner AI planes. Jet airliners have been left mostly as the default AI that comes with FS9.

I am familiar with the AI Aardvark web site and have some of their smaller jetliners waiting to take over AI duties. I don't have anything from World of AI so I don't know about the 755-200. Sorry. Perhaps try the .air and the aircraft.cfg files from the original equivalent AI Aardvark B755?

:wiggle:

Well, I didn't know that you meant a piston engine. Thanks anyway! The engine data in aircraft.cfg of this plane is in three parts (as follows):

...
[GeneralEngineData]
engine_type=1
Engine.0=4.750, -20.000, -2.500
Engine.1=4.750, 20.000, -2.500
fuel_flow_scalar=0.800
min_throttle_limit=-0.140000
...
[TurbineEngineData]
fuel_flow_gain=0.002
inlet_area=50.000
rated_N2_rpm=29920.000
static_thrust=42500.000
afterburner_available=0
reverser_available=1
...
[jet_engine]
thrust_scalar=1.000

I don't know if there is much to change these to make the plane fly better in high altitude.

Anyway this is no "big thing". Usually you look the AI plane only to take off or land (from short distance) and this goes ok with this one too.


Pekka

[Rich]

How about to much drag in the airfile I found this on a lot of origionaly non AI planes pressed into service as AI, the auto pilot is working overtime keeping up with it reduce the drag a bit and its fixed

[PHo17]

Sorry WoAI, AIA and others - my own fault. :redf:

I checked once more the flight plan files and found out that it was a different flight plan (I had already forgotten I had it still functioning) and AI plane I first thought.

If someone is interested the AI aircraft was an old PAI B752 (pai752v5.air) that didn't fly right. I replaced it with an AIA plane and that flies fine at high altitudes too. Propably PAI has found out this too, because they have a newer version of this plane too (no Finnair paint however).

Unfortunately the flight was a night flight, so I didn't notice the difference of the Finnair paints with AIA and PAI.

Pekka